RBG LED Throwie




Introduction: RBG LED Throwie

About: Professionally I have been a summer camp counselor, a Draftsman/designer, salesperson, bicycle mechanic, laminate flooring machine mechanic, teacher, and designer of the OP Loftbed. Personally I am a human t…

I came upon some color changing LEDs. I have seen multiple color LEDs before but not ones that changed on their own. I thought that these would be good to make throwies out of. If you do not know what a throwie is, it is basically a magnet, a battery, and an LED that you can throw and it attaches to a metal object. These are used as a sort of light graffiti. In this Instructable, I will show you how I made them including a solder free and solder versions. Since I first made this I also came up with a way to carry it....a ring:


Step 1: Tools and Supplies

The Supplies I bought in bulk.

The LED: https://amzn.to/2RUYwrK They are called slow rotating, but they do not rotate, they just alternate between the colors. They also come with 200 Ohm resistors.

The batteries: https://amzn.to/2tRrOQ7

The magnets: https://amzn.to/2t30vSC I used the 15mm Diameter and the other sizes can be used in other projects.

The tools I used were:

A soldering iron: https://amzn.to/3aTMYOm

Some flux core solder: https://amzn.to/37FLTr6

Helping hands: https://amzn.to/2RuSvD2

A multitool: https://amzn.to/36s4Z2E I only used it for the wire cutters.

As an alternative to soldering, I used a plastic welding kit: https://amzn.to/37vx62a

Step 2: Wrap the Resistor

You could make a throwie without a resistor, but using a resistor will make your battery last much longer. I used the 200 Ohm resistors that came with the LEDs. I wrapped one wire of the resistor around the cathode of the LED. I know some people will say to place the resistor on the anode, but I wanted mine to be on the negative side of the battery for the final assembly of the throwie.

Step 3: Solder

Be careful! Solder melts somewhere around 190^ C.

If you are going to solder the resistor on to the LED. Remember to heat what you are going to solder not the solder. Once the cathode of the LED and the resistor wire wrapped around it are hot enough, melt the solder onto them.

Step 4: Trim the Cathode

After soldering the resistor to the cathode of the LED, use wire cutters to trim off the excess cathode.

Step 5: Trim Before Liquid Plastic Welding

If you want you could choose to use ultraviolet liquid plastic weld instead of solder. I like to solder, but I know not everyone has a soldering iron or feels comfortable working with solder. The plastic weld I used held the connection tightly.

If you are going to use plastic welding, you will want to wrap one wire of the resistor around the LED cathode and then trim the excess cathode, before plastic welding.

Step 6: Ultraviolet Liquid Plastic Weld

Ultraviolet liquid plastic weld is like a glue. It is a liquid that stays a liquid until you expose it to ultraviolet light. There are a few different brands out there but I used Bondic. It is advertised as being an insulator and good for repairing cords, so I thought it might work as a substitute for solder. After wrapping the resistor tightly around the LED cathode and trimming off the excess cathode. Fold the resistor flat on the cathode and use the liquid plastic to glue the resistor to the wire wrapped Led cathode. I used the plastic weld on one side and then flipped it over to use it on the other side. Even after it cures, the plastic weld is clear, so I think it looks cool.

Step 7: Coil the Resistor Wire and Bent the LED Anode

To get the LED and resistor ready to assemble to the battery, Coil the free wire of the resistor and bend the anode of the LED. You want there to be a tight fit between the two wires and the battery.

Step 8: Assemble the Throwie

To assemble the throwie, Slip the 2032 battery between the anode of the LED and the wire of the resistor. Paying attention to the polarity of the battery. I used the 15mm diameter magnet to hold the cathode to the positive side of the battery and to give the throwie its magnetic abilities to adhere to ferrous surfaces.

Step 9: Experiment

You can use more than one LED per battery. One of the interesting things about the RBG LEDs is that they change color a little different pace from one another. So if you have two or more LEDs they will sometimes have their colors in sync and other times not. Have fun with your color changing throwies.

Step 10: Video

As usual, I made a video.

Thank you for watching.

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    1 year ago on Step 2

    Why would someone say to place the resistor on the anode? It does limit the current no matter on which side of the LED it is placed in line.


    Reply 1 year ago

    I have read some electronics books that say it should be on the anode. I think it does not matter...it will resist whichever side it is on. Thank you for the comment.


    1 year ago

    WOW! I did not know those things could change color. Amazing technology! Thanks for sharing.


    Reply 1 year ago

    I had not seen these before either. I just happened across them on Amazon. Thank you for the comment.


    Question 1 year ago on Introduction

    Hey, great project! Would the other 3V coin batteries work as well for this? I'm working on a project that would need a smaller diameter battery, i.e. 14mm or less where the 2032 is 19.5mm? Or do you know a source for that information? Thanks!


    Reply 1 year ago

    Thank you for the complement. Yes smaller 3V batteries would work. Good luck with your project. I would love to see a picture, when you are done.